WIP: support forwarding to multiple targets
This is a proof of concept of forwarding different domains to different recursive DNS providers to increase privacy / reduce centralization (from POV of the forwarding resolver).
From a quick test,
188.8.131.52 doesn't seem to like it for some reason and occasionally doesn't respond (observed with both 53/udp and 853/tls). Perhaps there's something weird with my network, but more testing is definitely required.